"OSLO -- Rising demand for energy, from biofuels to shale gas, is a threat to freshwater supplies that are already under strain from climate change, the United Nations said in a report on Friday.

It urged energy companies to do more to limit use of water in everything from cooling coal-fired power plants to irrigation for crops grown to produce biofuels.

"Demand for energy and freshwater will increase significantly in the coming decades," U.N. agencies said in the World Water Development Report. "This increase will present big challenges and strain resources in nearly all regions."

By 2030, the world will need 40 percent more water and 50 percent more energy than now, the report said. Water is under pressure from factors such as a rising population, pollution and droughts, floods and heatwaves linked to global warming."